Portable telephones of the type comprising a loudspeaker and a keypad to which is fixed a cover incorporating a microphone connected by conductors to a circuit situated inside the body, the cover being hinged to the body so that it can pivot between a position folded against the body and a position deployed away from the latter, are known in themselves.
When not in use, the cover is folded against the body and therefore protects the keypad on the body. In this configuration the portable telephone is of compact overall size and can therefore be easily placed in the pocket of a garment.
In use, the cover is deployed away from the body at a large obtuse angle to the body. In this configuration the microphone is exposed on the face of the cover that is on the same side as the face of the body carrying the loudspeaker.
The distance between the microphone and loudspeaker can be adjusted by increasing or reducing the angle between the body and the cover, so that it matches the distance between the ear and the mouth of the user.
The problem arises with this type of equipment of making an electrical connection between the microphone in the cover and the circuit in the body.
This electrical connection can be made by means of flexible electrical wires that can follow the rotation of the cover relative to the body.
A connection of this kind is not reliable, however.
The aim of the present invention is to create a portable telephone of the above type including electrical connections that can follow the rotation of the cover relative to the body in a reliable manner whilst being totally protected from dust in the environment and the detritus likely to be found in the pocket of a garment.
In accordance with the invention, this portable telephone is characterised in that the circuit and the microphone are electrically connected by at least one pair of rotary electric contacts incorporated into at least one of the hinges connecting the body to the cover.
Being incorporated into one of the two hinges connecting the cover to the body, these rotary contacts assure perfect and reliable transmission of the electric current whilst being mechanically and physically protected from the environment.
In one preferred version of the invention, the body and the cover being moulded, each pair of electric contacts comprises a first member in axial bearing engagement with a second member, each of the members being moulded into one of the two moulded material members constituting a hinge.
This moulding-in assures excellent electrical and mechanical protection of the rotary contact.
The two members are preferably pressed into axial bearing engagement with each other by a spring.
This axial bearing engagement assures a perfect electrical contact.
However, rotary contacts are subject to problems of wear, limited service life, and corrosion by the environment and by dust. It is consequently difficult to implement a rotary contact in which the contact resistance remains low in order to assure good conditions for the transmission of a weak current.
An other aim of the present invention is precisely to provide rotary contacts meeting the above conditions.
In accordance with the invention, these rotary contacts are characterised in that one of the members has a plane contact surface and the other member has a contact surface in axial bearing engagement with the aforementioned plane contact surface and that includes means producing a friction effect on rotation of the two members relative to each other.
In one advantageous version of the invention, the contact surface at the end of the other member incorporates asperities spaced from the rotation axis.
These asperities rub on the plane surface of the facing member to provide self-cleaning of the contact surfaces upon rotation.
Other features and advantages of the invention will emerge further from the following description.